Hypothermia is a condition of subnormal body temperature and presents serious consequences to the patient suffering therefrom. It has been shown that nearly seventy five percent of all patients who undergo surgical procedures develop hypothermia. This equates to approximately fourteen million patients a year in the United States alone. In the operating room, the hypothermic condition may be brought on by many factors including anesthesia, the air conditioning of the operating room, and the infusion of cold blood, I-V solutions, or irrigating fluids. Hypothermia is also a problem in the recovery room or PACU, as well as other areas in a hospital where room temperatures are kept cool and infusions of blood or other fluids may continue.
The prevention of hypothermia is especially important for pediatric care, because pediatric patients may be adversely effected by small changes in temperature. In particular, pediatric patients lose heat faster than adult patients because of their relatively low skin surface area to body mass ratio. Conversely, pediatric patients can also gain heat faster than adult patients. Therefore, pediatric patients are more susceptible to surgical complications, such as catching colds, from slight changes in temperature.
Several methods and products have been developed to help prevent hypothermia from occurring; such as the use of infrared lamps, cotton blankets, and warm water mattresses. However, none of these methods and products have proven completely successful. In fact, it has been shown that these methods and products can not even prevent the patients from losing their endogenous heat. (See Journal of Post Anesthesia Nursing, Vol. 5, No. 4, August 1990, pp 254-263).
Another method of helping to prevent hypothermia that has proven very effective is the use of forced warm air convection. As early as 1937, a refrigeration blanket using cold air convection was suggested in U.S. Pat. No. 2,093,834 to Gaugler. This blanket included a plurality of layers for channeling air flow from an inlet port. Non-inflatable portions were provided around the periphery of the blanket to secure the blanket around the body. Gaugler does not mention hypothermia treatment and does not suggest that the blanket could be used to supply warm air.
U.S. Pat. No. 2,512,559 to Williams also relates to a blanket for providing cooled air to a person. The blanket in Williams comprised a plurality of thin sheets of material connected together at a plurality of discrete locations and connected together in a continuous line about the peripheral edge. An air inlet was provided to communicate with space between the sheets to allow cool air to be supplied thereto. Again, no mention of hypothermia treatment or the supply of warm air is made.
In U.S. Pat. No. 4,572,188 to Augustine et al, a forced air convection system which can supply either cool or warm air to a blanket is described. The blanket in Augustine et al comprises a plurality of inflatable hollow tubes having their interiors connected together through transverse openings. An entry port is provided in the upper surface of the blanket for admitting the cool or warm air and small exit ports are provided through the lower surface to allow the cool or warm air to flow out toward a body covered by the blanket.
Other patents relating to the supply of cool or warm air to a person through an inflatable blanket include U.S. Pat. Nos. 4,660,388 to Greene, Jr.; 4,777,802 to Feher; and 4,867,230 to Voss. Each of these patents describe blankets having various attributes and configurations to supply cool or warm air to the person.
While some of the above systems suggest use in the operating room, they all possess similar disadvantages for such use. In particular, for the system to work in the operating room, the blanket must be attached to an air supply or blower unit through a hose. The placement of the hose during surgery can be crucial, as full access to the patient can be compromised if the hose must be located in a position which the surgeon, anesthesiologist or other surgical team member wants to occupy. In addition, the placement of the hose can create difficulties in locating other equipment such as I-V stands, monitors, etc. necessary for the surgical procedure. Moreover, it is important that the hose be as short as possible, because longer hoses lose more heat before delivery to the blanket, and thus overall effectiveness of the blanket is reduced.
Hose placement is not as critical in a non-operating room setting such as the PACU, ICU, or standard hospital room, but it is still desirable to have options for hose placement. This is especially true regarding the interspacial relationships between the blower unit and other equipment such as I-V stands, etc.
The prevention of hypothermia in pediatric patients requires special features and specifications. For purposes of this application, the term "pediatric" will be used to describe a number of patients, including neonates, infants, and children. In particular, the size of pediatric patients require that a relatively small blanket be provided which will still provide all of the warming advantages of a larger adult-sized blanket. Further, in certain surgical procedures, it is desirable to have the pediatric patient lie on top of the blanket because then the blanket is not in the way of the surgeon or other surgical team member. This requires the blanket to have sufficient air flow through the blanket to provide the warming therapy needed to prevent hypothermia.
None of the prior art noted above mentions use of blankets for pediatric patient care. Therefore, there remains a need in the art for improvements to forced warm air convection systems, especially for blankets which can be used in the treatment of pediatric patients.